Jyotiṣa or astronomy is one of the six Vedāṅgas or subsidiary sciences that help us to understand the Vedas. Since performance of sacrifices was the most important aspect of the Vedic religion and it was related to different periods of the year as also time and the position of the stars, a separate science called ‘Jyotiṣa’ was evolved in course of time. Each of the four Vedas developed its own Jyotiṣa.
The work Ātharvaṇa-jyotiṣa as extant today comprises 162 verses and may be a recast of an earlier work. It is generally assigned to the 2nd cent. B. C. It deals with muhūrta (a particular division of time), karaṇa (an astrological division of day), yoga (leading star of a lunar aste-rism; a variable division of time), tithi (lunar day) and vāra (day of the week). It is said to fall outside the Vedic period but before the period of the Siddhānta calendar which divides the zodiac into twelve rāśis or signs. It adopts a scheme of nakṣatra astrology. It forms nine groups of three nakṣatras (asterisms) each, the total being 27. Information is provided at length as to what should be done or not to be done on the presence of the nine groups and their constituents.
See also JYOTIṢA.